This section introduces aspects that may help facilitate a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
3GPP LTE (Long Term Evolution) uses channel aware scheduling on both the uplink and the downlink, meaning that the base station scheduler uses an estimate of the instantaneous channel state information in order to optimally schedule users and allocate data rates to them. The channel state information is made available to the base station scheduler through Channel Quality Indicators (CQI) fed back in the uplink by the mobile for scheduling in the downlink, and by periodic wideband Sounding Reference Signal (SRS) transmission by the mobile in the uplink for uplink scheduling.
When the Doppler of the mobile becomes high, the accuracy of the channel state information obtained from the CQI and the SRS becomes degraded, and performance degrades rapidly. The Doppler is related to the mobile speed through the relationship: Δ=fv/c, where f is the carrier frequency in Hz, v is the velocity of the mobile in meters per second, and c is the speed of light in meters per second. So the Doppler can become high if the mobile is moving at a higher speed for a given carrier frequency or is using a higher carrier frequency for a given speed.
Operators in the United States primarily own two carrier frequencies for 3GPP LTE, namely at a carrier frequency of 700 MHz and at a frequency of 2.1 GHz downlink/1.7 GHz uplink, the latter is called the Advanced Wireless Services (AWS) band. Similarly in Europe, operators will be deploying LTE in both the new 2.6 GHz band made available for LTE, but also eventually in lower frequencies such as the 900 MHz band as this spectrum is re-farmed from the currently used GSM.
New mechanisms and techniques that are able to help operators better utilize the different carriers on which they operate are clearly desirable and would advance communications generally.
Specific embodiments of the present invention are disclosed below with reference to FIGS. 1-3. Both the description and the illustrations have been drafted with the intent to enhance understanding. For example, the dimensions of some of the figure elements may be exaggerated relative to other elements, and well-known elements that are beneficial or even necessary to a commercially successful implementation may not be depicted so that a less obstructed and a more clear presentation of embodiments may be achieved. In addition, although the logic flow diagrams above are described and shown with reference to specific steps performed in a specific order, some of these steps may be omitted or some of these steps may be combined, sub-divided, or reordered without departing from the scope of the claims. Thus, unless specifically indicated, the order and grouping of steps is not a limitation of other embodiments that may lie within the scope of the claims.
Simplicity and clarity in both illustration and description are sought to effectively enable a person of skill in the art to make, use, and best practice the present invention in view of what is already known in the art. One of skill in the art will appreciate that various modifications and changes may be made to the specific embodiments described below without departing from the spirit and scope of the present invention. Thus, the specification and drawings are to be regarded as illustrative and exemplary rather than restrictive or all-encompassing, and all such modifications to the specific embodiments described below are intended to be included within the scope of the present invention.